Plankton samples are taken from a body of water by moving sample taking apparatus through a body of water. Such apparatus conventionally comprises a conical net having its smaller end secured to the open end of a sample collector which has at least one screened opening therein, the screen having a mesh through which water may flow outwardly of the container, but which is small enough to prevent plankton from passing through the screen. Examples of the conventional apparatus are disclosed in Phillips U.S. Pat. Nos. 4,089,131; 4,558,534; and 4,646,577.
The apparatus disclosed in the above identified Phillips patents functions satisfactorily, but experience has revealed the desirability of improvements. For example, each of the patented devices has a sample collector having a water outlet opening which is covered by a screen. Any water admitted to the container must flow outwardly through the opening therein. In areas where the plankton population is large, it is not uncommon for the screen to become clogged fairly quickly, thereby inhibiting the flow of water outwardly of the container and minimizing the efficiency of the sample taking process.
The recovery of plankton collected by the prior art apparatus necessitates taking the apparatus out of service until such time as the plankton that has been collected is removed from the collector. This is because the screen by means of which the plankton is collected must be cleared of the plankton before the apparatus again can be used to take further samples.
A principal object of this invention is to overcome the disadvantages of the known plankton sampling apparatus.